Motivated by Higgs Portal and Hidden Valley models, heavy particle dark matter that communicates with the supersymmetric Standard Model via pure Higgs sector interactions is considered. We show that a thermal relic abundance consistent with the measured density of dark matter is possible for masses up to $\sim 30\tev$. For dark matter masses above $\sim 1\tev$, non-perturbative Sommerfeld corrections to the annihilation rate are large, and have the potential to greatly affect indirect detection signals. For large dark matter masses, the Higgs-dark-matter-sector couplings are large and we show how such models may be given a UV completion within the context of so-called "Fat-Higgs" models. Higgs Portal dark matter provides an example of an attractive alternative to conventional MSSM neutralino dark matter that may evade discovery at the LHC, while still being within the reach of current and upcoming indirect detection experiments.
We consider electroweak singlet dark matter with a mass comparable to the Higgs mass. The singlet is assumed to couple to standard matter through a perturbative coupling to the Higgs particle. The annihilation of a singlet with a mass comparable to the Higgs mass is dominated by proximity to the W, Z and Higgs peaks in the annihilation cross section. We find that the continuous photon spectrum from annihilation of a perturbatively coupled singlet in the galactic halo can reach a level of several per mil of the EGRET diffuse gamma ray flux.
We examine a scenario where the Higgs boson is coupled to an additional singlet scalar field which we identify with a quintessence field. We show that this results in an unified picture of dark matter and dark energy, where dark energy is the zero-mode classical field rolling the usual quintessence potential and the dark matter candidate is the quantum excitation (particle) of the field, which is produced in the universe due to its coupling to the Higgs boson.
We show that fermionic dark matter (DM) which communicates with the Standard Model (SM) via the Higgs portal is a viable scenario, even if a SM-like Higgs is found at around 125 GeV. Using effective field theory we show that for DM with a mass in the range from about 60 GeV to 2 TeV the Higgs portal needs to be parity violating in order to be in agreement with direct detection searches. For parity conserving interactions we identify two distinct options that remain viable: a resonant Higgs portal, and an indirect Higgs portal. We illustrate both possibilities using a simple renormalizable toy …
High-energy $γγ$ colliders constitute a potential running mode of future $e^+ e^-$ colliders such as the ILC and CLIC. We study the sensitivity of a high-energy $γγ$ collider to the Higgs portal scenario to a hidden sector above the invisible Higgs decay threshold. We show that such $γγ$ collisions could allow to probe the existence of dark sectors through the Higgs portal comparatively more precisely than any other planned collider facility, from the unique combination of sizable cross-section with clean final state and collider environment. In addition, this search could cover the singlet Hi…
LHC constraints on Higgs-portal WIMPs are studied. Scalar, vector and anti-symmetric tensor fields are considered. They are assumed to be heavier than a half of the Higgs boson mass. We investigate 8 TeV LHC results on signatures of the vector boson fusion, mono-jet and associated production of the $Z$ boson, which proceed via virtual exchange of the Higgs boson. We show that Higgs-portal interactions of the vector and tensor WIMPs are constrained to be less than 0.43 and 0.16, respectively, while those for the scalar are very weak. Prospects of the 14 TeV LHC are also discussed.
We study effects from new colored states and the Higgs portal on gluon fusion production. We isolate possible loop contributions from new colored scalars, fermions, and vectors, incorporating effects from Higgs portal-induced scalar mixing, leading to dramatic effects on gluon fusion and branching fractions. Higgs identification must generally allow for these effects, and using our results, possible tensions from fits to the Standard Model expectation can be relieved by inclusion of New Physics effects.
We study an extension of the Inert Higgs Doublet Model (IHDM) by three copies of right handed neutrinos and heavy charged leptons such that both the inert Higgs doublet and the heavy fermions are odd under the $Z_2$ symmetry of the model. The neutrino masses are generated at one loop in the scotogenic fashion. Assuming the neutral scalar of the inert Higgs to be the dark matter candidate, we particularly look into the region of parameter space where dark matter relic abundance is primarily governed by the inert Higgs coupling with the leptons. This corresponds to tiny Higgs portal coupling of …
We perform a detailed study of scalar dark matter with triplet Higgs extensions of the Standard Model in order to explain the cosmic ray electron and positron excesses reported by AMS-02 and DAMPE. A detailed analysis of AMS-02 positron excess reveals that for different orderings (normal, inverted and quasi-degenerate) of neutrino mass, the hybrid triplet Higgs portal framework is more favored with respect to the single triplet Higgs portal for TeV scale dark matter. We also show that the resonant peak and continuous excess in DAMPE cosmic ray data can be well explained with the hybrid triplet…
We constrain the Higgs-portal model employing the vector-boson fusion channel at the LHC. In particular, we include the phenomenologically interesting parameter region near the Higgs resonance, where the Higgs-boson mass is close to the threshold for dark-matter production and a running-width prescription has to be employed for the Higgs-boson propagator. Limits for the Higgs-portal coupling as a function of the dark-matter mass are derived from the CMS search for invisible Higgs-boson decays in vector-boson fusion at 13 TeV. Furthermore, we perform projections for the 14 TeV HL-LHC and the 27…
We review predictions and constraints for nuclear recoil signals from Higgs portal dark matter under the assumption of standard thermal creation from freeze-out. Thermally created scalar and vector Higgs portal dark matter masses are constrained to be in the resonance region near half the Higgs mass or above several TeV. The resonance region for these models will be tested by XENONnT and LZ. The full mass range up to the unitarity limit can be tested by DarkSide-20k and DARWIN. Fermionic Higgs portal dark matter with a pure CP odd coupling is constrained by the Higgs decay width, but has stron…
The discovery of the Higgs boson opens the door to new physics interacting via the Higgs Portal, including motivated scenarios relating to baryogenesis, dark matter, and electroweak naturalness. We systematically explore the collider signatures of singlet scalars produced via the Higgs Portal at the 14 TeV LHC and a prospective 100 TeV hadron collider. We focus on the challenging regime where the scalars are too heavy to be produced in the decays of an on-shell Higgs boson, and instead are produced primarily via an off-shell Higgs. Assuming these scalars escape the detector, promising channels…
In a number of Higgs-portal models, an $SU(2)$ isospin-singlet scalar boson generically appears at the electroweak scale and can mix with the Standard Model (SM) Higgs boson with a mixing angle $α$. This singlet scalar boson can have renormalizable couplings to a pair of dark matter particles, vectorlike leptons or quarks, or new gauge bosons, thereby modifying the Higgs signal strengths in a nontrivial way. In this work, we perform global fits to such models using the most updated LHC Higgs-boson data and discuss the corresponding implications on Higgs-portal-type models. In particular we fin…
We consider a Dirac singlet fermion as thermal dark matter for explaining the X-ray line in the context of a supersymmetric Higgs-portal model or a generalized Dirac NMSSM. The Dirac singlet fermion gets a mass splitting due to their Yukawa couplings to two Higgs doublets and their superpartners, Higgsinos, after electroweak symmetry breaking. We show that a correct relic density can be obtained from thermal freeze-out, due to the co-annihilation with Higgsinos for the same Yukawa couplings. We discuss the phenomenology of the Higgsinos in this model such as displaced vertices at the LHC.
The Higgs portal to scalar Dark Matter is considered in the context of non-linearly realised electroweak symmetry breaking. We determine the interactions of gauge bosons and the physical Higgs particle $h$ to a scalar singlet Dark Matter candidate $S$ in an effective description. The main phenomenological differences with respect to the standard scenario can be seen in the Dark Matter relic abundance, in direct/indirect searches and in signals at colliders.
We perform frequentist and Bayesian statistical analyses of Higgs- and Z-portal models of dark matter particles with spin 0, 1/2 and 1. Our analyses incorporate data from direct detection and indirect detection experiments, as well as LHC searches for monojet and monophoton events, and we also analyze the potential impacts of future direct detection experiments. We find acceptable regions of the parameter spaces for Higgs-portal models with real scalar, neutral vector, Majorana or Dirac fermion dark matter particles, and Z-portal models with Majorana or Dirac fermion dark matter particles. In …
In the Higgs portal framework, the Higgs field generally mixes with the Standard Model singlet leading to the existence of two states, one of which is identified with the 125 GeV scalar observed at the LHC. In this work, we analyse direct and indirect constraints on the second mass eigenstate and the corresponding mixing angle. The existence of the additional scalar can be beneficial as it can stabilise the otherwise-metastable electroweak vacuum. We find parameter regions where all of the bounds, including the stability constraints, are satisfied. We also study prospects for observing the dec…
We explore an extension of the Standard Model by an additional U (1) gauge group and a complex scalar Higgs portal. As the scalar is charged under this gauge factor this simple model supplies a vector dark matter candidate satisfying the observed relic abundance and limits from direct dark matter searches. An additional Higgs-like state, that may be heavier or lighter than the observed Higgs, is present and satisfies LEP and LHC bounds whilst allowing for absolute stability of the electroweak vacuum in a range of parameter space.
We present Higgs-Portal dark matter (DM) models to explain the reported Galactic Center GeV gamma-ray excess. Naive effective theories are inconsistent with direct detection constraint for the relevant parameter range. Simple extended models with dark gauge symmetries can easily accommodate the gamma-ray excess through the Higgs-Portal coupling while satisfying various constraints.
The hypothesis of dark matter interacting with the standard model uniquely via the Higgs portal is severely challenged by experiments. However, if dark matter is a fermion, the Higgs-portal interaction implies the presence of mediators, which can change the phenomenology significantly. This article discusses the impact of weakly-interacting mediators on the dark-matter relic abundance, direct detection, and collider searches. At the LHC, a typical signature of Higgs-portal fermion dark matter features soft leptons and missing energy, similarly to gaugino production in models with supersymmetry…
We study a model of spin-1 dark matter which interacts with the Standard Model predominantly via exchange of Higgs bosons. We propose an alternative UV completion to the usual Vector Dark Matter Higgs Portal, in which vector-like fermions charged under SU(2)$_W \times$ U(1)$_Y$ and under the dark gauge group, U(1)$^\prime$, generate an effective interaction between the Higgs and the dark matter at one loop. We explore the resulting phenomenology and show that this dark matter candidate is a viable thermal relic and satisfies Higgs invisible width constraints as well as direct detection bounds.
We study the sensitivity of future electron-positron colliders to UV completions of the fermionic Higgs portal operator $H^\dagger H \bar χχ$. Measurements of precision electroweak $S$ and $T$ parameters and the $e^+e^- \to Zh$ cross section at the CEPC, FCC-ee, and ILC are considered. The scalar completion of the fermionic Higgs portal is closely related to the scalar Higgs portal, and we summarize existing results. We devote the bulk of our analysis to a singlet-doublet fermion completion. Assuming the doublet is sufficiently heavy, we construct the effective field theory (EFT) at dimension-…
The Higgs portal to scalar Dark Matter is considered in the context of non-linearly realised electroweak symmetry breaking. We determine the dominant interactions of gauge bosons and the physical Higgs particle $h$ to a scalar singlet dark matter candidate. Phenomenological consequences are also studied in detail, including the possibility of distinguishing this scenario from the standard Higgs portal in which the electroweak symmetry breaking is linearly realised. Two features of significant impact are: i) the connection between the electroweak scale $v$ and the Higgs particle departs from th…
Higgs portal interactions provide a simple mechanism for addressing two open problems in cosmology: dark matter and the baryon asymmetry. In the latter instance, Higgs portal interactions may contain the ingredients for a strong first order electroweak phase transition as well as new CP-violating interactions as needed for electroweak baryogenesis. These interactions may also allow for a viable dark matter candidate. We survey the opportunities for probing the Higgs portal as it relates to these questions in cosmology at the LHC and possible future colliders.
We revisit the Higgs portal vector dark matter model including a hidden sector Higgs field that generates the mass of the vector dark matter. The model becomes renormalizable and has two scalar bosons, the mixtures of the standard model (SM) Higgs and the hidden sector Higgs bosons. The strong bound from direct detection such as XENON100 is evaded due to the cancellation mechanism between the contributions from two scalar bosons. As a result, the model becomes still viable in large range of dark matter mass, contrary to some claims in the literature. The Higgs properties are also affected, the…
Mono-$X$ signatures are a powerful collider probe of the nature of dark matter. We show that mono-Higgs and mono-$Z$ may be key signatures of pseudo-scalar portal interactions between dark matter and the SM. We demonstrate this using a simple renormalizable version of the portal, with a Two-Higgs-Doublet-Model as electroweak symmetry breaking sector. Mono-$Z$ and mono-Higgs signatures in this scenario are of resonant type, which constitutes a novel type of dark matter signature at LHC.
We study the Higgs portal from the Standard-Model to a hidden sector and examine which elements of the extended theory can be discovered and explored at the LHC. Our model includes two Higgs bosons covering parameter regions where the LHC will be sensitive to two, one or none of the particles at typical discovery luminosities for Standard Model Higgs production.
In a scenario of Higgs portal dark matter, Higgs exchange processes are essential for both dark matter annihilation in the early Universe and direct search experiments. The CDMS II collaboration has recently released their final results on direct dark matter searches. We study a scalar dark matter model with multi-Higgs doublets under the constraint from the CDMS II results and also from the WMAP data. We find that the possible maximal value for the branching ratio of the invisible decay of the Higgs boson can be significantly greater than that in the Higgs portal model with one Higgs doublet,…
In the Standard Model (SM), the Higgs mass around 125 GeV implies that the electroweak vacuum is metastable since the quartic Higgs coupling turns negative at high energies. I point out that a tiny mixing of the Higgs with a heavy singlet can make the electroweak vacuum completely stable. This is due to a tree level correction to the Higgs mass-coupling relation, which survives in the zero-mixing/heavy-singlet limit. Such a situation is experimentally indistinguishable from the SM, unless the Higgs self-coupling can be measured. As a result, Higgs inflation and its variants can still be viable…
We investigate a Higgs portal dark matter model by extending the Standard model (SM) with a complex singlet, $S=(s+ia )/\sqrt{2}$, where $a $ is a dark matter candidate and $S$ gets no vacuum expectation value but $s$ mixies with the SM Higgs via a trilinear interaction. We point out an interesting scenario, where only quartic coupling contributes to the dark matter relic abundance and there is no tree level contribution to the direct detection. Numerical analysis shows that the direction detection cross section, which arises at the one-loop level, is about $2\sim 5$ orders below the current L…
In these proceedings, we report on the possible signatures of a light scalar WIMP, a dark matter candidate with M_DM ~ few GeV, which is supposed to interact with the Standard Model particles through the Higgs, and which might be related to the annual modulation observed by DAMA.
A review of the Higgs portal-vector dark matter interpretation of the spin-independent dark-matter nucleon elastic scattering cross section is presented, where the invisible Higgs decay width measured at the LHC is used. Effective Field Theory and ultraviolet complete models are discussed. LHC interpretations show only the scalar and Majorana dark-matter scenarios; we propose to include interpretation for vector dark matter in the EFT and UV completions theoretical framework. In addition, our studies suggest an extension of the LHC dark matter interpretations to the sub-GeV regime.
The simplest Higgs-portal dark matter model is studied in the light of dark matter self-interacting effects on the formation of large scale structures. We show the direct detection limits on the resonant and large mass regions. Finally, we also compare these limits with those at the LHC and Xenon 1T experiments.
We investigate catalysis of electroweak baryogenesis by fermionic Higgs portal dark matter using a two Higgs doublet model augmented by vector-like fermions. The lightest neutral fermion mass eigenstate provides a viable dark matter candidate in the presence of a stabilizing symmetry Z_2 or gauged U(1)_D symmetry. Allowing for a non-vanishing CP-violating phase in the lowest-dimension Higgs portal dark matter interactions allows generation of the observed dark matter relic density while evading direct detection bounds. The same phase provides a source for electroweak baryogenesis. We show that…
We study the implications of non-standard Higgs Yukawa couplings to light quarks on Higgs-portal dark matter phenomenology. Saturating the present experimental bounds on up-quark, down-quark, or strange-quark Yukawa couplings, the predicted direct dark matter detection scattering rate can increase by up to four orders of magnitude. The effect on the dark matter annihilation cross section, on the other hand, is subleading unless the dark matter is very light -- a scenario that is already excluded by measurements of the Higgs invisible decay width. We investigate the expected size of corrections…
We consider an extended inflation model in the frame of Higgs portal model, assuming a nonminimal coupling of the scalar field to the gravity. Using the new data from Planck $2013$ and other relevant astrophysical data, we obtain the relation between the nonminimal coupling $ξ$ and the self-coupling $λ$ needed to drive the inflation, and find that this inflationary model is favored by the astrophysical data. Furthermore, we discuss the constraints on the model parameters from the experiments of particle physics, especially the recent Higgs data at the LHC.
A muon jet ($μ$-jet) is a very special feature that consists of a cluster of collimated muons from the decay of a fast moving light particle of mass about $\mathcal{O}$(1 GeV). We will use this feature to search for very light particles from rare decays of the Higgs boson. For such a small angular separation of muons which might come from a long-lived particle, both ATLAS and CMS could have the displaced-vertexing-reconstruction capability. We use two simple models of the Higgs-portal type to explore the possibilities of event topologies with two $2μ$-jets, one $2μ$-jet $\&$ one $4μ$-jet, and …
The Higgs sector of the Standard Model offers a unique probe of the hidden sector. In this work, we explore the possibility of renormalizable Higgs couplings to the hidden sector vector fields which can constitute dark matter (DM). Abelian gauge sectors with minimal field content, necessary to render the gauge fields massive, have a natural Z_2 parity. This symmetry ensures stability of the vector fields making them viable dark matter candidates, while evading the usual electroweak constraints. We illustrate this idea with the Stueckelberg and Higgs mechanisms. Vector DM is consistent with the…
Higgs portal dark matter (DM) models are simple interesting and viable DM models. There are three types of the models depending on the DM spin: scalar, fermion and vector DM models. In this paper, we consider renormalizable, unitary and gauge invariant Higgs portal DM models, and study how large parameter regions can be surveyed at the International Linear Collider (ILC) experiment at $\sqrt{s}=500$ GeV. For the Higgs portal singlet fermion and vector DM cases, the force mediator involves two scalar propagators, the SM-like Higgs boson and the dark Higgs boson. We show that their interference …
We propose a scenario of the right-handed neutrino dark matter in the context of the minimal gauged $U(1)_{B-L}$ model by introducing an additional parity which ensures the stability of dark matter particle. The annihilation of this right-handed neutrino takes place dominantly through the s-channel Higgs boson exchange, so that this model can be called Higgs portal dark matter model. We show that the thermal relic abundance of the right-handed neutrino dark matter with help of Higgs resonance can match the observed dark matter abundance. In addition we estimate the cross section with nucleon a…
We consider the impact of new exotic colored and/or charged matter interacting through the Higgs portal on Standard Model Higgs boson searches at the LHC. Such Higgs portal couplings can induce shifts in the effective Higgs-gluon-gluon and Higgs-photon-photon couplings, thus modifying the Higgs production and decay patterns. We consider two possible interpretations of the current LHC Higgs searches based on ~ 5/fb of data at each detector: 1) a Higgs boson in the mass range (124-126) GeV and 2) a `hidden' heavy Higgs boson which is underproduced due to the suppression of its gluon fusion produ…
Dark matter that was once in thermal equilibrium with the Standard Model is generally prohibited from obtaining all of its mass from the electroweak phase transition. This implies a new scale of physics and mediator particles to facilitate dark matter annihilation. In this work, we focus on dark matter that annihilates through a generic Higgs portal. We show how partial wave unitarity places an upper bound on the mass of the mediator (or dark) Higgs when its mass is increased to be the largest scale in the effective theory. For models where the dark matter annihilates via fermion exchange, an …
In this paper, we construct two component dark matter model and revisit fine-tuning, unitarity and vacuum stability problem in this framework. Through Higgs-portal interactions, the additional scalar and vector singlet field can interact with the SM particles. The parameter space of the model are severely constraint by observed relic density and direct detection experiments. We found that, unlike the SM, the fine-tuning problem is relaxed due to the modified Veltman condition. The vacuum stability problem is addressed, the additional contributions from two DM singlets to the $β$ function make …
We study the impact on leptogenesis of Higgs portal couplings to a new scalar singlet. These couplings open up additional $CP$-violating decay channels for the higher mass singlet neutrinos $N_2$ and $N_3$. We analyze the simplest case of two-level $N_1-N_2$ leptogenesis, including significant mass hierarchies, in which the $CP$ asymmetry is generated in part by singlet-mediated decays of $N_2$. For these models, provided the lightest singlet neutrino $N_1$ is sufficiently weakly coupled to avoid excessive washout, its mass scale is not directly constrained by the Davidson-Ibarra bound.
We show that the Higgs portal interactions involving extra dark Higgs field can save generically the original Higgs inflation of the standard model (SM) from the problem of a deep non-SM vacuum in the SM Higgs potential. Specifically, we show that such interactions disconnect the top quark pole mass from inflationary observables and allow multi-dimensional parameter space to save the Higgs inflation, thanks to the additional parameters (the dark Higgs boson mass $m_ϕ$, the mixing angle $α$ between the SM Higgs $H$ and dark Higgs $Φ$, and the mixed quartic coupling) affecting RG-running of the …
As an educational aid and source for expert information, a web portal dedicated to Higgs boson research is presented. A database is created with more than 1000 relevant articles using CERN Document Server API and web scraping methods. The database is automatically updated when new results on the Higgs boson become available. Using artificial intelligence and natural language processing, the articles are categorized according to properties of the Higgs boson and other criteria. The process of designing and implementing the Higgs Boson Portal (HBP) is described. The components of the HBP are dep…
In the so-called Planckian Interacting Dark Matter (PIDM) scenario, superheavy dark matter particles are produced after inflation by gravity-mediated interactions through the freeze-in mechanism. In the minimal PIDM model, the absence of any additional direct coupling with Standard Model particles is assumed. However, for scalar dark matter particles there is no symmetry that suppresses the Higgs portal coupling. In this paper, we therefore study the impact of a non-zero interaction with the Higgs field on the PIDM paradigm for scalar dark matter. In particular, we fully explore the model para…
We study under which conditions a scalar particle is a viable WIMP Dark Matter candidate with Higgs and dilaton interactions. The theory is a composite Higgs model with top partial compositeness where both the Higgs and the Dark Matter candidate arise as pseudo Goldstone boson of the coset SO(6)/SO(5) from a new physics sector. We highlight the role of the dilaton in direct and indirect searches. We find that a Dark Matter particle with a mass around 200-400 GeV and a relatively light dilaton are a fair prediction of the model.
Many models of Higgs portal Dark Matter (DM) find themselves under pressure from increasingly tight direct detection constraints. In the framework of gauge field DM, we study how such bounds can be relaxed while retaining the thermal WIMP paradigm. When the hidden sector gauge symmetry is broken via the Higgs mechanism, the hidden sector generally contains unstable states which are lighter than dark matter. These states provide DM with an efficient annihilation channel. As a result, the DM relic abundance and the direct detection limits are controlled by different parameters, and the two can e…
This article is an addendum to Ref.~\cite{Baek:2014jga}. Here, we discuss the invisible Higgs decay width $Γ_{h}^{\rm inv}$ in the Higgs portal vector dark matter (VDM) model in the limit $m_V \rightarrow 0^+$. In the effective field theory (EFT) approach where the VDM mass is attributed to the Stückelberg mechanism, $( Γ_{h}^{\rm inv} )_{\rm EFT}$ is divergent, which is unphysical and puzzling. On the other hand $( Γ_{h}^{\rm inv} )_{\rm UV}$ becomes finite in a UV completion, where the VDM mass is generated by the dark Higgs mechanism. Then we can take the limit $m_V \rightarrow 0^+$ by taki…
A coupling of a scalar, charged under an unbroken global U(1) symmetry, to the Standard Model via the Higgs portal is one of the simplest gateways to a dark sector. Yet, for masses $m_{S}\geq m_{H}/2$ there are few probes of such an interaction. In this note we evaluate the sensitivity to the Higgs portal coupling of di-Higgs boson production at the LHC as well as at a future high energy hadron collider, FCC-hh, taking into account the full momentum dependence of the process. This significantly impacts the sensitivity compared to estimates of changes in the Higgs-coupling based on the effectiv…
We investigate resonant di-Higgs production as a means of probing extended scalar sectors that include a 125 GeV Standard Model-like Higgs boson. For concreteness, we consider a gauge singlet Higgs portal scenario leading to two mixed doublet-singlet states, h_1,2. For m_h_2 > 2 m_h_1, the resonant di-Higgs production process p p -> h_2 -> h_1 h_1 will lead to final states associated with the decaying pair of Standard Model-like Higgs scalars. We focus on h_2 production via gluon fusion and on the b b tau^+ tau^- final state. We find that discovery of the h_2 at the LHC may be achieved with ~ …
The Higgs-portal model with a singlet scalar Dark Matter particle is one of the simplest extensions to the Standard Model that can reproduce the relic density. Unfortunately this model is strongly constrained by direct and indirect DM detection, as well as by collider physics. Most of the parameter space is already ruled-out and the rest will be explored in the next future. We show that a simple extension of the DM sector with a second scalar singlet enables a substantial opening of the allowed window in the parameter space.
A scalar particle with a relic density set by annihilations through a Higgs portal operator is a simple and minimal possibility for dark matter. However, assuming a thermal cosmological history this model is ruled out over most of parameter space by collider and direct detection constraints. We show that in theories with a non-thermal cosmological history Higgs portal dark matter is viable for a wide range of dark matter masses and values of the portal coupling, evading existing limits. In particular, we focus on the string theory motivated scenario of a period of late time matter domination d…
High-luminosity fixed target experiments provide impressive sensitivity to new light weakly coupled degrees of freedom. We revisit the minimal case of a scalar singlet $S$ coupled to the Standard Model through the Higgs portal, that decays visibly to leptons for scalar masses below the di-pion threshold. The dataset from the LSND experiment is found to impose the leading constraints within two mass windows between $m_S \sim 100$ and 350 MeV. In the process, we analyze a number of scalar production channels in the target, finding that proton bremsstrahlung provides the dominant channel at LSND …
